The present invention relates generally to communication devices, and more particularly, to temperature control of communication devices.
Many communication devices, including wireless communication devices, have electronic modules or components that are capable of generating a significant amount of heat during normal operation. Portable two-way wireless radio communication devices, capable of voice and data communications, are commonly subject to continuous transmission of information, according to various packet data communication protocols, that can exacerbate the amount of heat generated by these electronic modules or components. Such wireless radio communication devices will typically include a radio-frequency power amplifier (RF PA) that operates to amplify radio signals that are to be transmitted by an antenna of the radio. Power amplifiers are characteristically inefficient and high capacity RF-PA""s can generate a substantial amount of heat, particularly under continuous transmission conditions, which may not be adequately dissipated by a device heat sink or other heat dissipation mechanism, even if the heat sink is located in close proximity to the RF PA. With the trend to miniaturize communication devices continuing unabated, these heat sinks or other heat dissipation mechanisms that are provided to dissipate heat from heat-sensitive modules all too often prove to be inadequate to the task. When the heat generated by such electronic modules or components exceeds the heat dissipation capability of the communication device, critical heat-sensitive modules of the communication device, such as the RF PA and surrounding heat-sensitive components of the device, may be easily damaged.
Controlling device temperature of a heat-sensitive module of a communication device typically relies upon a priori information about the thermal characteristics of the heat-sensitive module, commonly referred to as the thermal profile of the heat-sensitive module, that is stored in the communication device. U.S. Pat. No. 5,519,886, issued May 21, 1996 to Gilbert et al., for instance, discloses the use of a priori thermal information to control a heat-sensitive module. This approach, however, presents various problems that the present invention seeks to overcome. First, the thermal characteristics of the heat-sensitive module must be profiled and stored in permanent storage before the device can operate. Second, because the thermal profile of the module is static and unchanging, it does not allow for the natural aging of device modules or components over time. Third, the thermal profile cannot include time periods of previous transmissions of the device, defined by start and stop times, and this information must be updated during operation of the communication device. Fourth, the stored profile is simply an approximation of the actual thermal profile during operation and thus the accuracy of the thermal profile is directly proportional to the size of the storage space dedicated to the profile. Moreover, the stored thermal profile contains thermal characteristics only for a particular heat-sensitive module of the communication device and thus the thermal profile is not readily applicable for other modules. Typical RF PAs for portable two-way wireless radio communication devices, for instance, come in a wide variety of designs and power ratings, from 2 Watts to 22 Watts and higher, for instance, and so the thermal profile for an RF PA rated at 22 Watts of a certain design and manufacturer would not necessarily be applicable to an RF PA rated at 2 Watts of another design and manufacturer. Fifth, because it is not practical to store an unlimited number of thermal profiles that would be representative of each of the possible operating conditions to which the module might be subjected, the stored data points of the profile are used to derive various points along the thermal profile that correspond to the current operation conditions of the module. These thermal profile calculations are processor-intensive operations that require interpolation and approximation techniques that are inherently prone to round-off error.
There is therefore an unmet need in the art to be able to control the temperature of a communication device, particularly those increases in the temperature of heat-sensitive modules or components that are attributable to transmission conditions of the communication device, in a manner that overcomes the various shortcomings of the prior art.